Heat transfer apparatus



April 24, 1945.

H. J. DE N. MccoLLuM 2,374,608

HEAT TRANVSFER APPARATUS Filed Aug. 15, 1942 2 Sheets-Sheet l l 70,95 o CoM/7,6555 oe April 24, 1.945. H. .LDE N. MccoLLuM 2,374,608

HEAT TRANSFER APPARATUS Filed Allg. 15, 1942 2 SheeiS-Sheet 2 Patented Apr. 24, 1945 i 2,374,608 naar TRANSFER APPARATUS lliieiiry J. :Be N. McCollum, Chicago, Ill.; Thelma McCollum rexecutrix of McCollum, deceased said Henry J. -De N.

`pplcatitm August 15, 1942, -ISeI-al No. 454,915

venting the production of a flame in the atinosi phere at the outlet ofthe exhaust stacks of aircraft engines, particularly` on 'military aircraft; These exhaust gases ordinarily discharge to the 'atmosphere at a temperature 'between 14010 F. and 1500 F., and, since, especially when the engineis operating at high power output, theexhaust gases contain large 'amountsof unconsumed vaporized gasoline, the production of a torchlike flame at the outlet lends of the exhaust stacks i.

t cannot be avoided. Admixture of the atmospheric air with the exhaust gases while they are flowing through the stack merely lresultsin` further combustion and thus increases thetemperature ofthe exhaust gases. The usual method of arresting names, as `by passing theA combustible gases through a wire mesh or `wire-gauze (as employed in the conventional miners safety lamp) cannot feasibly be used in aircraft exhaust stacks because any such structure placed in an exhaust stack would practically instantaneously be heated to such a high temperature that it would become ineffective as aame arrester.

In vorder to 'be effective, a name arrester `operat-` ing onthis principle would have to dissipate a large proportion of the waste heat of the exhaust gases, and, since between 3,000,000 and 3,500,000 B. t. u. perhour are passed to the atmosphere with the exhaust gases as waste heat from a 1000 hp. engine, it will be apparent that an ex tremely large and heavy conventional type of heat exchanger would be requiredv in order Vto reduce the temperature of theexhaust gases 'below their ignition temperature.

As distinguished from conventional types of heat exchangers in which the heat is 'transferred from one fluid to 'another by conduction `through a Wall separating the two fluids, the heat transfer apparatus of my invention operates upon the principle of physically conveying the heat energy from one of thelfluid mediums to the other. By utilizing this principle, apparatus may readily be constructed which is capable of transferring heat from oneluid medium toV another at `an extremely high rate without `requiring that the apparatus be heavy or'bulky. v f

It is `thus an object of my invention to provide an improved apparatus for the rapid transfer of heat from -one iuid medium to another.

A further object `is `to provide `an improved means for preventing th'e burning of 'the exhaust gases from an internal combustion engine `as they are discharged into the atmosphere; i

` A further object ijs to provide an improved system and apparatus for heating the cabins of airplanes and vthe like,lutilizing the engine `exhaust gases as a source of heat.

Affurther `object is to `provide an improvedheat exchanger of high heat 'transfer capacity which is simple inconstruction, and light in weight.

A `further object is to lprovide an improved ap paratus for' utilizing the heat contained in the exhaust ,gases of an ,internal combustion engine.

A further object is to provide an improved apparatuslfor the purpose of the elimination of flames at ,the outlet ends of .the exhaust stacks, and for providing heat for the heating of the cabin, for heating surfaces to prevent icing, .and for other uses.

A Vfurther Objectis to provide an improved .apparatus .for transferringheat `from `a gaseous iiuid containing noxious gases to jair for heating and Ventilating purposes, in which the possibility of 4escape of the noxious .gases to the `Ventilating airis avoided.

Other objects will appear from the .following description, reference `being. had to the accompanying drawings, in which:

Fig. l is a somewhat diagrammatic longitudinal sectional view of ioneform of theheat transfer apparatus;

Fig. 2 is a transverse sectional` view thereof taken on the line 2 2 of Fig. 1;

Fig. A3 is a .somewhat diagrammatic longitudinal sectional view of the improved .hea-t transfer apparatus incorporated in the exhaust stack of anairplane -for the prevention of fname rcoinbustion of the -exhaustgases .as they emerge-into the atniosphene.;

Fig.. `4 Iis -a transverse sectional view taken -on Eig, 5 is a transverse :sectional View of .axmozdined :form :of the `invention which the Vheat invention shown in Fig. 8, portions thereof being shown in fragmentary section.

Referringfto Figs. l and 2, the invention is illustrated as embodied in an apparatus for transferring heat from the exhaust gases of an internal combustion engine to a stream of air to be heated. In this gure, the exhaust gases flow through a generally rectangular conduit I0 in the direction indicated by the arrows, while the air to be heated flows through -a similar conduit I2. These conduits are spaced apart, and mounted for rotation between them is a rotary heat transfer member comprising a plurality of discs I4 secured to a drum I5. The drum I6 is carried by a shaft I8 mounted for rotation in a pair of antifriction bearings 2@ carried by suitable supporting members 22. The discs III project through thin slots 24 formed in the conduit Ill and through similar slots 2 formed in the conduit I2. These slots are of length corresponding to the chords at which the inner wall surfaces of the conduits I and I2 intersect the circular discs, and are made as narrow as possible, while permitting free rotation of the discs I4 through the slots.

This clearance between' the edges of the slots and the discs is made as small as possible, since these clearances form paths for the escape of gases of combustion from the conduit I0 and for escape of air from the conduit I2. The discs are preferably made of metal, and for the example illustrated, where the discs project into a conduit containing products of combustion from an internal combustion engine, they are preferably of a metal which is not corroded by such gases, such as stainless steel. These discs' I4 are made as thin as is compatible with their maintaining their flat shape. It will be noted, however,'in this respect, that the discs may rotate at a fairly high speed so that the centrifugal forces acting on the discs will tend to keep the-m flat.

In operation, the heat transfer apparatus of Figs. 1 and 2, will be effective to transfer a large proportion of the 'heat from the exhaust'gases flowing through the conduit IE! to the air flowing through the Ventilating air conduit I2. The space between the conduits is preferably inthe slip stream of the airplane so that any leakage of exhaust gases through the slots 2li cannot possibly enter the slots 26 and the conduit I2.

As further assurance against such leakage of gases of combustion into the -conduit I2, the air owing in the latter is preferably maintained at a pressure above that in the space between the two conduits so that any leakage will be outwardly from the conduit I2 rather than in the reverse direction.

As the exhaust gases owing in the conduit IIJ pass the portions of the discs I4 which project into this conduit, they will radiate and conduct heat to these portions of the discs. In addition, the flowing gases will, due to friction, cause the discs It, drum I6, and shaft I8, to rotate in the bearings 2li. Such rotation will normally be `at such velocity that the lineal speed of the periphery of each of the discs Ill will be somewhat less than that of the speed of the exhaust gases, with the result that there will be some scouring action of the exhaust gases against the surfaces of the discs, thereby to improve the rate of heat transfer from the exhaust gases to the discs. As

the heated portions of the discs pass from thev conduit IEB through the slots 2li, their surfaces will be scoured by the flow of the atmospheric air of the slip stream of the plane in the space between the conduits I0 and I2 will lose some of its heat, but it will still be at a relatively high temperature as it enters the conduit I2, where it will impart a large proportion of its heat to the air owing through this conduit. There is preferably some difference in lineal speed between the air owing through the conduit I2 and the peripheries of the discs I so that there will be a high coefcient of heat transfer between the discs and such air. In passing from the conduit I2 to the conduit I0, each incremental portion of the discs I4 is further cooled by the air flowing in the space between the conduits so that as each incremental portion of a disc enters the conduit II), it will be at a relatively low temperature.

The apparatus is preferably so designed that the discs I4 -will rotate at a speed such that as each incremental portion leaves the conduit I it will be at a temperature which is the arithmetical mean between the temperature of the exhaust lgases approaching the discs I4 and the temperature of the air approaching these discs. In any event, the discs I4 should rotate at such speed that there is considerable relative motion between the surfaces of these discs and the gases flowing in the conduits I0 and I2. If the effect of the friction of the exhaust gases upon the surfaces of` the discs I4 is, as above indicated, relied upon to cause rotation of the discs,A

they will necessarily lag behind the combustion gases and provide such relative motion.

Assuming that the exhaust gases approaching the rotating discs are at a temperature of 1500 F., and that the air in the conduit I2 approaching the discs Iltis at a temperature of l0 F., the incremental portions of the discs I4 as they leave the conduit IIJ, should be at a temperature of 755 F., which, assuming a hundred per cent eflciency of transfer of heat from the exhaust gases to the discs, would mean that the exhaust gases would leave the discs at the same temperature of 755 F. 'I'he transfer of` heat from the exhaust gases to the discs, while not one hundred per cent eiiicient, is so eiiicient that these exhaust gases are reduced considerably be? low the temperature at which the fuel vapor contained therein will ignite when the exhaust gases are projected into the atmosphere. Therefore, any flame within the conduit I0 is ex'nv tinguished as the products of combustion flow past the discs lli, and the possibility of reignition is eliminated, and as a result, itis impossiblefor a flame to be produced at the yendof the exhaust stack.

This type of heat transferringapparatus may be used for conveying heat from one uid to fanother in a large variety of different systems, for

example, one of thefluids (i. e., thatflowing-` porcelain, various plastic materials, or alloys,

depending upon the nature of the fluids to and from which heat is to be transferred, and de` pending upon the temperature ranges of `the fluids, and their diiference in temperature-because in this type f apparatus, it is not esaccrocs.

i `highfspeeirlcfheat,and be a :good radiator of heat.

In some instances, it maybedesirable yto provide the .-discswit-hia surface 'nn-ish` to :improve the ability of the surface to receive and emit Aradiant heat. l

upon .an airplane, the conduit I2 may be located withinthe fuselage of the plane, While `the con-` duit-Ill may-,comprise the exhaust stack and be located externally of the fuselageV and spaced some distance therefrom so that someof thetair oftheslipstream will iiow past the discs I4 to scouranygaseous impuritiesfrom the surfaces of these ydiscs as the incremental portionsemerge from the conduit Ill. As previously indicated, when the conduit I2 is utilized torsupplying Ventilating air, itis :preferably under surncient` pressure at ythe slots 26 that leakage: will "be outwardly from the conduit ratherV than in the reverse direction. l The invention as illustrated in Fig. 3 isutilized for the purpose `of cooling the exhaust gases in the exhaust stack ofan airplane. Inthis :em-

bodiment of the invention, the exhaust `gases flowthrough a manifold passageway 36 to the rotor 32'of a turbo-supercharger, the `bearings and casing of this supercharger being cooledby atmos-j pheric air admitted through a small air ram pipe 34.` Theturbo-supercharger is merely ldiagrammatically illustrated and may be` of any usual construction which utilizes the kinetic `energy of the products of combustion to provide power for driving the engine superchargeraor for other purposes. i The exhaust gases are discharged from the supercharger through a conduit 36, which is preferably generally rectangular in cross sectional area and has slots 38 formed therein to receive a plurality of discs suitably mounted upon hubs 42 non-rotatably secured to a shaft 44. The shaft 44 is mounted for free rotation in anti-friction bearings 46. The exhaust gases thus flow between the upper portions ofthe discs 40 which extendwithin the conduit 36 and are discharged tothe atmosphere through an outlet 48. It will be noted that substantially half of each of the discs lies within the conduit i 36, whereas, the remaining portion of each of these discs is within the slip stream. Even though the major portion of each of the discs lies in the slip stream, the discs will usually rotate clockwise, that is, against the air stream and with the exhaust gases because of the greater velocity of the latter. However, under low speed cruising conditions, the rate of exhaust gas flow tially as great as that of the remainder of the stack, there will be no substantial increase in back pressure due to the use of the invention. In fact, `since the exhaust gases are cooled by the discs 4U, their Volume is reduced and as a result, the backpressure may be reduced instead of increased. i

In such instances as it is not feasible` to use the energy of the iiuids ilowing through the con- .installing thefapparatus ,of Figs-'l 1 `and `2 ifi duits as a .for :rotating the Iheat' 'transter discs, a construction :suchas showninFig. L5 may be: :employed In this embodiment 4.of the `invention,` the .parts maybe constructed in the .same manner yas |shown in Figs. r1 and 2. 1v1-"arts:shown imFga which maybe identical with-those disclosed andxdescribed with .reference `to Figs.. 1 and i,2,; have therefore had corresponding refer' encepcharactersapplied thereto. 'I'he shaft I8 vis coupled `to a ,motorfl which .may be supplied with electrical energy .from pany vsuitable source, the motor being supported by `a `pair of brackets 52 t connected `respectively with the conduits |20 and `I 2Y so `as, :toqmaintain the discs I=4 properly positioned `within the yslotst24 `and `26. The apparatus .of Fig. 5 maythus be used when the rate oftuidiiowthrough the conduits `I2 and I-IJ Yis notosuliciently rapid` to cause rotation of the,

,'lhis construction is `alsoof,utilitywhen an ex` actl temperature control is desired( While lthe motor `5l] will normally be `a constant :speed .mo-`

tor, it may be la, variable Aspeed motor whenever,`

temperaturezcontrol :of the fluid iiow through one or the other ofthe conduits is desired, sincethe rateoi `hea-t transfer will in` general andjwithin limits, be dependent upon the speed` of rotation of ,the-discs. Thus, by varying the `speed .of the motor; the temperature of one or the other of the` fluids may be controlled, and such control maybe effected by suitable `thermostat-ic means wheneverrequired. l

` When the fluid tio-wthrough the conduits is at such `low Velocity as not to ybe readily capableof rotating discs such as I4 due to the frictional drag, and particularly when it is not essential to transfer an extremely large quantity of heat from one fluid to the other, a construction s uch as shown in Figs. 6 and 7 may be employed. In this embodiment of the invention, one of the fluids flows through a ring-sector-shaped conduit 60, while the other fluid Hows through a similarly shaped conduit 62, the flow through these conduits preferably being in the same direction, especially if the fluids are iiowing at api maybe suliciently low that the slip stream will proximately 'the same Velocity. The heat exchanger comprises a rotor mounted upon a shaft 64, a hub portion 66, spokes 61, rim 68, and fan 10. The shaft 64 is mounted in suitable antifriction bearings 'I2 for free rotation. The blades 'I0 are adapted to pass through a slot 'I6 formed in the conduit 60 and a slot 'I8 formed in the conduit 62.

Assuming that the rotor `is rotating` clockwise (Fig. 6),.the amount of heat `transferred from the fluid flowing in conduit 60 to the fluid flowing in conduit 62 depends no1; only upon the speed of rotation of the rotor, but also upon the angular propinquity of conduits 6U and 62, as well as the temperature of the air or other medium between l the conduits 60 and 62.

`conduits and a considerable portion or the iiuid flowing through these conduits to the atmosphere. This type of heat transfer apparatus is therefore of the most utility where the iluids flowing in the conduits are air or other gases 'Whose escape and dilution is of no importance.

A simple modification of the invention shown in Figs. 8 and `9 comprises a foraminous disc 80, i1- lustrated as a screen, mounted upon a spindle 82 rotating in suitably supported anti-friction bearings. 83. :Fluid to be cooled is directed toward the disc tthrough a conduit 84, the end of which is conformed asindicated in Fig. 9 to tend to force thefluid through the openings in the disc B0. Air to be heated is forced under` some pressure through a conduit 86, the end of which is beveled to conform to the plane of the disc 80. Air flowing from the conduit 86, after passing through -the disc 80, enters a continuation 81 of the conduit 86, the conduit 81 leading to a place at which the heated air is to be utilized. The kinetic energy of the gases discharged from the conduit :84, which may be the exhaust stack of an internal combustion engine, strikes the foraminous disc 80 at an angle so as to cause the latter to rotate. As each incremental section of the foraminous disc 80 is heated by the exhaust gases, it moves to the space between the conduit sections 8.6 and 81 so as to heat the air flowing-from the former to the latten The disc 80 may be a screenror a perforated metal disc. The screen will be effective to pick up heat from the exhaust gases more rapidly than the perforated plate because of the greater surface area of metal exposed to Athe exhaust gases by the wires of which the screen is woven. However, the screen is more fragile than the perforated disc, and if the screen is made of a metal which is even slightly corrodible by the exhaust gases, the screen will, of course, be less durable than a perforated disc.

yThe underlying principle of operation of the apparatus of Figs, 8 and 9, is essentially the same as that of the previously described embodiments, namely, that a body absorbs heat in moving throughthe path of iiow of a hot fluid and gives up its heat in moving through the path of flow of another body of fluid, with the possibility that the body may be cleansed of any adhering gas by passing through a third fluid medium intermediate its movement through the other two mediums.

While I have shown and described certain illustrative embodiments of my invention, and such showing has been in somewhat diagrammatic form, it will be apparent to those skilled in the art that the invention may be embodied in a wide variety of different types of apparatus in which it is desired to raise or lower, or both,`

the illustrative forms of Athe invention shown; l

but desire to include within the scope of the following claim all such variations and modications by which substantially the results of myinvention may be obtained through the use of' substantiallythe same or equivalent means.

I claim:

For use in an airplane powered by an internal combustion engine and having an exhaust stack for the discharge of exhaust gases from the ven gine to the atmosphere, means for loweringthe temperature of the exhaust gases below their ignition temperature comprising, a foraminous disc mounted for rotation in a-plane at an angle to the direction of now of the exhaust gases and driven at high speed by the exhaust gases in the manner of a turbine, incremental portions vof at the outletl end of said exhaust stack is prevented.

' HENRY J. DE N. MCCOLLUM. 

